Viscometric Study on Polystyrene/polydimethylsiloxane Blends in Various Solvents

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1 Asian Journal of Cheistry Vol. 19, No. (7), Viscoetric Study on Polystyrene/polydiethylsiloxane Blends in Various Solvents OMAR MELAD*, OMAR ABU-TEIM and EHAB SOBEH Departent of Cheistry, Al-Azhar University, P.O.Box 177, Gaza, Palestine The viscoetric easureents were carried out for polystyrene (PS), polydiethyl siloxane (PDMS) and PS/PDMS in three different solvents at 5 C. The results showed that the choice of solvent is believed to play a key role in characterizing the viscosity behaviour of the polyer solution. The intrinsic viscosity and the viscoetric interaction paraeters have been erientally easured for the binary (solvent/ polyer) as well as for the ternary systes and also theoretically evaluated for the latter. The estiation of the copatibility degree in the different solvents have been done by eans of the signs of b and [ η]. The results show that the copatibility of PS/PDMS blend in toluene while incopatibility in THF and benzene, respectively. Key Words: PS/PDMS blend, Polyer copatibility, Different solvents, Dilute solution viscoetry. INTRODUCTION The study of viscosity on a ternary syste which is coposed of two different polyers and a solvent is a very interesting subject, ainly due to its siplicity and iportance in the characterization of the interolecular interaction between the two different polyers in solution Dilutesolution viscoeter (DSV) is the best technique for polyer-polyer copatibility study aong the other techniques, which are tieconsuing and erientally deanding 19. The effectiveness of this ethod relies on the assuption that the attractive or repulsive interolecular interaction between two polyers in solution (polyer (1)- polyer () interaction) have a great influence on the viscosity of the polyer solution. The two polyers are dissolved in a coon solvent, so that their hydrodynaic volues are affected by the solvent selected. The interolecular interaction between the two different polyers in solution ay also play a key role in characterizing the viscosity behaviour of ternary syste to which little attention has been devoted -. As it is well known that the interolecular interaction in polyer solution of binary syste (polyer (1)-solvent) can be either repulsive or attractive depending on the solvent selected, for exaple, if a given polyer was

2 884 Melad et al. Asian J. Che. dissolved in a solvent at a teperature above θ, the segents of a given polyer would repel one another and the repulsive interolecular interaction should be ected. On the other hand, if the polyer was dissolved in a solvent at teperature below θ, the segents of the polyer would attract one and the attractive interolecular interaction should be ected. Therefore, in order to perfor dilute solution viscoetry easureents, the influence of solvent on the interolecular interaction between the two different polyers in solution should be also taken into account. In this work, the viscosity easureent of PS, PDMS and PS/PDMS blends in different solvent (benzene, toluene and THF) are presented. The copatibility of the polyer ixture is evaluated through the signs of b and η. [ ] EXPERIMENTAL Polystyrene (PS) with average olecular weight 5, g/ol and polydiethyl siloxane (PDMS) with average olecular weight of 95, g/ol were purchased fro Aldrich (USA). Benzene, Toluene and THF were purchased fro laboratory cheicals Riedel-de Haen (Gerany) and used as received. Viscoetric easureents: All easureents were perfored at 5 ±.1 C using a canon-fenske type capillary viscoeter. The stock solutions of each ternary or binary syste were ade by dissolving the polyer saples in filtered solvents (benzene, toluene and THF) up to concentration of 1. g/dl. Five saple solutions of lower concentrations were prepared by adding appropriate aliquots of solvent to the stock solution. For each solution, 1 L of the solution was loaded to iniize drainage errors to the viscoeter and placed in the therostat. The elution tie of each solution was then deterined as the average of several readings. The dilution finished after the solution volue reached 1 L. Kinetic energy corrections were taken into account for the evaluation of the intrinsic viscosity [η] and viscoetric interaction paraeter (b), which were deterined by extrapolation to infinite dilution (zero solute concentration) and fro the slope of the linear plots, respectively, Huggins plots, i.e. η sp /c vs. c. RESULTS AND DISCUSSION The reduced viscosity of the binary or ternary polyers in solution follows the linear relationship given by Huggins equation: ( η ) sp c i i = [ η] i + biici (1)

3 Vol. 19, No. (7) Viscoetric Study on PS/PDMS Blends 885 Krigbau and Wall developed the following equation for ixed polyer solution 18. sp, η = [ η ]C + [ η ]C + b C + b C + b C C () where η sp, is the specific viscosity of polyer solution, [η ] and [η ] are the intrinsic viscosity of polyer coponents and, respectively and b and b are the specific interaction paraeters of coponents and in binary syste (polyer-solvent). b is the specific interaction paraeter of coponents and in solution (ternary syste) which can be ressed according to Willason and Wright 15, b = (b b ) 1/ () has been used when the viscoetric paraeters of the two hoo polyers are positive and : b = (b + b )/ (4) When one or both of the take a negative value. Eq. () can be ressed in a weight-average for since after soe atheatical procedure 4 the general for b is: 1/ 1/ b b = b w + b + b w w (5) Generally, eq. (4) is used to define the eal value of the viscoetric interaction paraeter, between chains of both polyers in the ixture. To avo the erroneous fro the values of b in eq. (4) depending on the signs of the viscoetric interaction paraeter, a new viscoetric interaction paraeter, b, which can be defined as: b = b w + b w (6) Which copared with eq. (4) eliinates the uncertainly of defining the b paraeter. On the other hand, the eriental value of b is given by parallelis as: b = bw + bw + b w w (7) where b, b and b are obtained fro the slop of eq. (1) for binary and ternary systes, respectively. Therefore the first copatibility criterion, () proposed in this paper, is as follows: Copatibility if b = (b b ) > or, b > b and incopatibility if b = (b b ) < or () b < b. The second copatibility criteria based on the difference between the eriental and the eal values of [η], therefore, it would be copatible if [ η] = ([ η] [ η] ) < and incopatible if [ η] = ([ η] [ η] ) >, where [η] is deterined fro the intercept of the plots of eq. (1) and [η ] can be calculated by using the atheatical derivations 4 which can be seen in the flowing equation: [η] = [η] w + [η] w (8)

4 886 Melad et al. Asian J. Che. The intrinsic viscosities as well as the viscoetric interaction paraeters for the different binary systes at 5 C are copiled in Table-1. Fro this table, it is observed that the PS or PDMS in different solvents have a negative value of b which akes it ipossible to calculate the b according to eq., so we can neglect this paraeter if we use b ( ) criteria. The values of the intrinsic viscosity for PS or PDMS in THF is a better solvent for PS and PDMS, therefore, the polyer-solvent interaction THF is larger than in toluene or benzene, which lead to swelling of the polyer chains in solution and thus increases the intrinsic viscosity of the polyer solution. Fig. 1 shows the plots of the reduced viscosity hsp/c vs. c for PS/PDMS blends with weight fractions of.,.5,.5,.75 and 1. in benzene, toluene and THF, respectively at 5 C. All the plots are linear. On extrapolating hsp/c vs. zero concentration, both [η] and the viscoetric interaction paraeter (b), can be obtained for the ternary polyer syste, which are tabulated in Table-. The [η] values of PS in binary polyer solution are larger than [η] values of PS/PDMS ternary polyer solution at different weight fractions and in different solvent as shown in Table-. A reasonable lanation is that the repulsive interactions between PS and PDMS in different solvents would increase the interolecular excluded volue and the contraction of PS/PDMS coils in solvent and thus decrease the [η]. TABLE-1 VISCOSITY DATA FOR POLYSTRYENE AND POLYDIMETHYL SILOXANE IN DIFFERENT SOLVENTS AT 5 C [η] (dl/g) b (dl/g) [η] (dl/g) b (dl/g) Solvent Benzene Toluene THF PS PS PDMS PDMS The next step has consered of evaluating the agnitudes that ake it possible to establish the degree of copatibility in the polyer ixture. ( ) ( ) The first criteria is b deterined with values of b and b which are tabulated in Table-. Using eqs. 1-5, the second criteria is [η] evaluated through the difference between [η] and [η] which are tabulated in Table-. Fig. shows the variation of a) b and b) [η] with different weight fractions of PS and PDMS ixtures in benzene, toluene and THF, respectively. The inforation about therodynaic interolecular interactions between polyer () and () should obtained fro coparison between eriental b fro eq. 1 and () b values fro eq. 5 by ean of a paraeter b. Negative values of b are found for solutions of systes containing incopatible polyers, while positive ones indicate attractive interaction and copatibility. In the hypothetical case that

5 Vol. 19, No. (7) Viscoetric Study on PS/PDMS Blends 887 b =, it would signify that chains interact neither favourably nor unfavourably 14,5-7. It can be seen fro Fig. that the sae behaviour is obtained with the two criteria, within a certain degree, PS is copletely copatible with PDMS in toluene in all coposition ranges which PS incopatible with PDMS in THF and benzene in all coposition ranges. The incopatibility between PS and PDMS in THF and benzene could be attributed to the strong repulsive interolecular interactions between the polyer chains in THF and benzene, where all values of b are negative and [η] are positive. TABLE- EXPERIMENTAL AND THEORETICAL VISCOMETRIC DATA FOR THE TERNARY MIXTURE PS/PDMS IN DIFFERENT SOLVENTS AT 5 C Solvent W [η Benzene Toluene THF ] b [η ] b () (a) η sp/c c (g/dl) w= w=.5 w=.5 w=.75 w=1 (b) η sp/c c (g/dl) w= w=.5 w=.5 w=.75 w=1

6 888 Melad et al. Asian J. Che (c) η sp/c C (g/dl) w= w=.5 w=.5 w=.75 w=1 Fig. 1. Reduced viscosity dependence on polyer ixture concentration and Huggins Linearization at different weight fractions of PS for the ternary syste (a) Benzene(1)/PS()/PDMS(), (b) Toluene(1)/PS()/PDMS() and (c) THF(1)/PS()/PDMS() at 5 C. -. b W Benzene Toluene THF.4. [η] W Benzene THF Toluene Fig.. Plots of different copatibility agnitude as a function of ixture coposition for the polyer ixture in different solvents

7 Vol. 19, No. (7) Viscoetric Study on PS/PDMS Blends 889 Conclusion The interolecular interaction between PS and PDMS in solution is greatly associated with the solvent fro which PS/PDMS blends dissolved. In Toluene, the attractive interolecular interaction between PS and PDMS existed; on the contrary, in either THF or benzene, the repulsive interolecular interaction between PS and PDMS existed. These different interolecular interactions can be used to interpret the phase behavior of PS/ PDMS blends cast fro different solvents. REFERENCES 1. Y.C. Zhang, J.S. Qian, Z. Ke, X.C. Zhu, H. Bi and K.M. Nie, Eur. Poly. J., 8, ().. S. Saha, Eur. Poly. J., 7, 51 (1).. Y. Haiyang, Z. Pingping, H. Minjun, M. Shengli and W. Yuanyuan, Eur. Poly. J., 6, 949 (). 4. R. Garcia, O. Melad, C.M. Goez, J.E. Figueruelo and A. Capos, Eur. Poly. J., 5, 4 (1999). 5. M. Mathew, K.N. Ninan and S. Thoas, Polyer, 9, 65 (1998). 6. A.A. Abdel-Azi, W.Y. Bourtos and E.M. Abdel-Bary, Polyer, 9, 54 (1998). 7. A.A. Abdel-Azi, A.W Atta, M.S. Farahat and W.Y. Boutros, J. Appl. Poly. Sci., 69, 1471 (1998). 8. W.H. Jiang and S.J. Han, J. Poly. Sci. Part B: Poly. Phys., 6, 175 (1998). 9. I. Katie, E. Dias and R. Valenciano, Eur. Poly. J., 4, 55 (1998). 1. R. Garcia, C.M. Goez, I. Porcar, J.E. Figueruelo and A. Capos, Eur. Poly. J.,, 17 (1997). 11. I. Inaura, K. Akiyaa and Y. Kubo, Poly. J., 9, 119 (1997). 1. Z.H. Sun, W. Wang and Z.L. Feng, Eur. Poly. J., 8, 159 (199). 1. K.K. Chee, Eur. Poly. J., 6, 4 (199). 14. B. Boher, D. Berek and S. Florian, Eur. Poly. J., 6, 471 (197). 15. G.R. Williason and B. Wright, J. Poly. Sci.: Part A,, 1985 (1996). 16. E.H. Castiff and W.A. Hewett, J. Appl. Poly. Sci., 6, 96 (196). 17. L.H. Cragg and C.C. Biegelow, J. Poly. Sci., 16, 177 (1955). 18. W.R. Krigbau and F.T. Wall, J. Poly. Sci., 5, 55 (195). 19. O. Olabisi, L.M. Robeson and M.T. Shaw, Polyer-Polyer Miscibility, Acadeic Press, New York (1979).. E.G. Crispi, A.F. Rubria and E.C. Muniz, Polyer, 4, 519 (1999). 1. H. Yang, P. Zhu, S. Wang, Y. Zeng and Q. Guo, Eur. Poly. J., 6, 1 ().. S. Wu, F. Zheng, F.X. Li and Z. Tong, Eur. Poly. J., 6, 679 ().. P.J. Flory, Principles of Polyer Cheistry, Ithaca, Cornell University Press, New York (195). 4. N.V. Mikhailov and S.G. Zelikean, Kollo Zh., 19, 465 (1957). 5. K.S. Shih and C.L. Beatty, Br. Poly.,, 11 (1991). 6. C.M. Goez, J.E. Figueruelo and A. Capos, Macrool. Che. Phys.,, 46 (1999). 7. M. Bohdanecky and J. Kovar, Viscosity of Polyer Solutions, Elsevier Scientific, Asterda (198). (Received: 18 April 5; Accepted: June 6) AJC-59